Biotechnology has lent its helping hand in producing natural-flavor materials that are obtained as pure or complex mixtures of individual flavor compounds. Examples of pure mixtures include esters, alcohols, lactones, acids, ketones, and aldehydes. Biotechnological methods are used in the production of lactones, which play an important role in the flavor industry. Microorganisms undergo fermentation process thereby hydroxylating fatty acids to produce lactones. For example, lipase produced by Candida antarctica converts certain cyclic ketones to corresponding lactones through the Baeyer-Villiger reaction.
Lactone- A Preview
Being ubiquitous, lactone has been isolated from major food systems. Lactones that occur naturally and organoleptically contain either Υ- or δ- structure and are straight-chained.
Some lactones are even macrocyclic. Aliphatic lactones play a major role as food aroma components, which are based on their organoleptic properties. Some of the properties include peachy, oily, coconut, nut, honey, fruity, creamy, and much more. Since their threshold of odor is low, averaging around 0.1 ppm, lactones have potential flavor value. Υ-lactones primarily occur in plants, while δ-lactones are predominantly found in animal products.
Lactones of high sensory value have 8 to 12 carbon atoms among which are a few important food flavor components such as apricots, fermented foods, strawberries, milk products, and peaches. These sensory lactones are produced in minimal amounts when a fruit ripens in a plant. This is usually due to the catabolic process involving fatty acids.
However, absolute configuration and optical purity vary depending on the presence of identical lactones, which are isolated from many sources.
The lactose biosynthesis process is a complex one and is implicated by the following five systems:
(1) from corresponding keto acids through NAD-linked reductases;
(2) from unsaturated fatty acids through hydration;
(3) from fatty acid hydroperoxides through lipoxygenase reaction;
(4) from naturally occurring esters;
(5) through enzymatic cleavage of hyrdoxy fatty acids that can form lactones; elucidate whether the lactones are intracellularly formed and excreted or whether the hydroxy acids undergo immediate lactonisation after being released from the cell.
A wide array of microorganisms performs the biosynthesis of de novo lactone. Examples of microbially produced lactones include: 5-Decanolide from Candida globiformis; 4-
Decanolide from Ceratocystis moniliformis; 4-dodecanolide from Pityrosporum species; 4-hexanolide from Ischnoderma benzoinum; 4-pentanolide from Polyporus durus; and 5- olide from Sporobolomyces odorus to name a few. In terms of flavor, the important Υ- and δ-lactones are accessible through biotechnology. These lactones are economically viable and are related to dodecanioc, octanoic, and decanoic acids. Out of the six major lactones, Υ-decalactone or the decanolide are important.
4-decanolide in found in dairy products and fruits such as peaches. This lactone has fatty-oily, creamy, and fruity attributes and is produced by both biotransformation and biosynthesis. Biotransformation process yields high when compared to the biosynthesis route and hence plays a major commercial role. 4-Decanolide is produced by biodegradation of ricinoleic acid using the microorganism Yarrowia lipolytica. The ricinoleic acid undergoes β-oxidation to form 4-hydroxydecanoic acid. The produced 4-
Decanolide has high optical purity and contains 98 percent of (+)-R-enantiomer. Natural 4- Decanolide plays a major role in the flavor industry.
5-Decanolide occurs naturally in white wine, butter, coconut, and in fruits such as strawberries, peaches, and raspberries. This lactone exhibits sweet, milk-like, coconut, and creamy flavor. Coriolic acid undergoes β-oxidative degradation to obtain 5-Decanolide. The microorganism responsible for this biotransformation process is the Cladosporium suaveolens. Another method is to produce intermediates of hydroxy fatty acids via
Scientists are performing research to microbial hydroxylation of a fatty acid. It is also known that certain Mucor species produce Υ- and δ-lactones from their corresponding ethyl esters or fatty acids. Lactones produced via such microbial transformations are known to have high enantiomeric purity.
Ester hydrolyses of enzymes in an aqueous media catalyse transesterification or esterification reactions in biphasic water-organic or monophasic-organic solvents. There are many well-known processes in enzymatically synthesizing lactones including: (1) intramolecular esterification; (2) enantioselective hydrolysis; and (3) Baeyer-Villiger reaction.
In general, the flavor industry has accepted biotechnology as an important part of the industrial process. Enzymatic and microbial biotechnology has been introduced by numerous flavor houses. Progresses have been seen in the production of lactone, most of which has achieved industrial success. The success of lactone is attributed to the low toxicity of compounds toward the biocatalytical systems.
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